int stepCount = 30;
color to, from;

void setup() {
  size(300, 300);
  from = color((int)random(255), (int)random(255), (int)random(255));
  to = color((int)random(255), (int)random(255), (int)random(255));
}

void draw() {
  fill(from);
  rect(0, 0, width/2, height/2);
  fill(to);
  rect(width/2, 0, width/2, height/2);
  
  for (int i = 0; i < stepCount; i++) {
    float step = (float) i/stepCount;
    println(step);
    fill(lerpColor(from, to, step));
    rect(i*(width/stepCount), height/2, (width/stepCount), height);
  }
}